The present invention generally relates to medical devices. Specifically the invention relates to skin mounted electrodes with substantially short nano spikes that are easily attachable to human skin. More specifically, the invention relates to electrodes that provide substantially positive and reliable contact without the need for using gels, shaving and/or sanding of the skin surface to enable positive electrical electrode attachment.
Epidermal attachments for physiological data collection such as ECG and EEG sensing and transdermal delivery of peptides, proteins, various agents and drugs to the human body are some of the medically useful applications for skin mounted medical devices. Some of these devices require mechanical disruption of the skin in order to enhance transdermal flux such as disclosed in U.S. Pat. No. 3,814,097 issued to Ganderton et al, U.S. Pat. No. 5,279,544 issued to Gross et al, U.S. Pat. No. 5,250,023 issued to Lee et al., and U.S. Pat. No. 3,964,482 issued to Gerstell et al. These devices typically utilize tubular or cylindrical structures generally, although the Gerstell invention uses an array of solid or hollow microneedles to penetrate through the stratum corneum into the epidermal layer, but not to the dermal layer. PCT applications WO 97/48440, WO 97/48441, and WO 97/48442 by Cormier et al employ a plurality of solid metallic microblades and anchor elements, etched from a metal sheet, with a length of 25-400 mm. PCT application WO 96/37256, by Godshall discloses another microblade structure with blade lengths of 10-20 mm for enhancing transdermal delivery.
Another example of a needle that penetrates into the dermis is provided in U.S. Pat. No. 5,591,139, WO 99/00155, and U.S. Pat. No. 5,855,801 all issued to Lin. These patents and publications disclose how the needles are processed using integrated circuit fabrication techniques. The needles used have a length in the range of 1,000 to 6,000 microns.
U.S. Pat. No. 5,309,909 issued to Gadsby et al., discloses a combined skin preparation and monitoring electrode. The electrode is designed to reduce motion artifacts in recording biopotentials by penetrating a patient""s skin prior to acquiring biopotentials. Penetration of the skin reduces the skin impedance and the skin""s propensity to generate motion artifacts. The electrode includes a resilient dome with penetration tines extending from the concave inner surface of the dome. Upon application of a force, the dome moves from a first position to second position forcing the penetration tines into a patient""s skin. Upon removal of the force, the dome moves back to its original configuration withdrawing the penetration tines from the patient""s skin.
U.S. Pat. No. 5,197,471 issued to Otero, discloses a dry electrode for medical use to record existent biopotentials on the skin surface and for electrical stimulation of different zones of the human body. The dry electrode comprises a flexible electro-conductive plate provided on its bottom side with a plurality of sharp bosses for partial skin penetration. The plate includes a corrugated radial extension tongue and two orifices, the first orifice in the center of the plate and a second orifice in the tongue portion. The orifices in the tongue portion allow for different connectors to be utilized, such as a stem with a circular base, a Stillson wrench or a hook type connection. The electrode makes contact on its bottom face with a needle that penetrates and stays anchored within the skin.
U.S. Pat. No. 4,311,152, issued to Modes et al., discloses a medical electrode and skin preparation device adapted to be secured to the skin and designed to prepare the skin by penetration of the epidermal layer of the skin in contact with the electrical conductor of the electrode after the electrode is secured in place on the skin. The electrode includes an abrading member associated with an electrical conductor capable of transmitting biopotential events for recording, with the electrical conductor retained by a collar and an adhesive-coated pad securing the electrode to the skin of the patient. The abrading member in contact with the skin is movable relative to the skin of the patient and collar by an applicator gun so as to allow penetration of the epidermal layer of the skin after the electrode is placed on the skin. Uniform skin preparation achieved by the electrode and applicator gun minimizes motion artifacts arising from skin potential variations.
U.S. Pat. No. 5,701,895, issued to Prutchi et al, discloses an implantable subcutaneous data port for transferring data received from a sensor implanted within a subject. The data port electrically connects to the sensor and includes a control circuit electrically connected to an access port. The control circuit includes a current loop transmitter that modulates a current loop signal with voltage outputs from the sensor. Needle electrodes (large minimum diameter) are insertable through the skin of the subject to the access port and provide an electrical interface between the control circuit and current loop receiver.
U.S. Pat. No. 6,050,988, issued to Zuck, discloses a device including a sheet member having a plurality of microprotrusions extending from a bottom edge for penetrating the skin of a patient. The sheet member, when in use, is oriented in an approximately perpendicular relation to the patient""s skin. The microprotrusions penetrate the body surface to create good agent conduction from the system into the body or vice versa. Also, the microprotrusions or microblades are generally formed from a single piece of material and are sufficiently sharp and long for penetrating at least the stratum corneum of the skin.
U.S. Pat. No. 5,458,141, issued to Neil, discloses a medical electrode and a skin preparation device adapted to be secured to the skin of a patient and designed to prepare the skin by abrasion or penetration of the epidermal layer of the skin in contact with the conductive means of the electrode after the electrode is secured in place on the skin. The electrode includes a penetrating device associated with a conductor capable of transmitting biopotential events for recording, with the conductor being retained by an adhesive member that secures the electrode to the skin of the patient. The penetration device in contact with the skin is movable relative to the skin of the patient and a holder by an applicator gun to abrade or penetrate the epidermal layer of skin after the electrode is placed on the skin. Uniform skin preparation is achieved by a flexible screen member and electrolyte gel reservoir on the electrode and an applicator gun that minimizes motion artifacts arising from skin potential variations.
PCT publication WO 98/25517, by Svedman, discloses a device for sensing bioelectrical signals. Specifically, the invention relates to an electrode device that utilizes negative pressure and preferably heat to a portion of the epidermis causing interstitial fluid and/or the epidermal basement membrane to contact an electrode for a measuring operation.
Attachment devices exist for fixing EEG electrodes to a patient""s scalp. These devices may use colloidal glue, adhesive tape or bandages. EEG electrodes may also be attached by incorporating them into web matrix helmets. Placing and removing these EEG electrodes from a patient""s scalp is time consuming. The EEG electrodes are uncomfortable to wear and may lose signal contact during extended ambulatory monitoring. A quick-placement EEG electrode is described in U.S. Pat. No. 6,201,982 issued to Menkes and referenced herein in its totality. This patent proposes the continued use of gel as well as several connecting devices to replace current electrodes to ensure positive electrode contact.
Further, there is a need for a smart patch as described in U.S. Pat. No. 6,200,265 issued to Walsh and Thompson, which is incorporated herein by reference in its entirety. The patch electrode in the ""265 patent describes the reception of uplink telemetry but it also requires, for at least one of its embodiments, the sensing of the ECG signal. The patch is easily attachable to a human skin to enable communication with medical devices and body bus systems as described in U.S. Pat. Nos. 4,987,897 and 5,113,859 issued to Funke, which are incorporated herein by reference in their entirety. Similarly, a smart patch can also enable communication with medical devices and body wave systems as described in U.S. Pat. No. 6,115,636 issued to Ryan, which is incorporated herein by reference in its entirety. In addition, a smart patch may be used to detect ECG signals for use in association with electrogram signals for identifying whether a lead is properly positioned during the operative implant procedure, as described in U.S. Pat. No. 6,161,039 issued to Krichen et al., which is incorporated herein by reference in its totality. Similarly and as would be easily evident to those skilled in the art, a smart patch might also be used to acquire ECGs for use in pacemaker and defibrillator follow-up sessions, troubleshooting post-implant, and transtelephonic monitoring, among others.
In PCT applications WO 97/48440, WO 97/48441, and WO 97/48442, to Cormier, the delivery of large molecule drugs through the skin is disclosed. Specifically, the disclosures relate to a non-conducting inert set of microblades to puncture the dead tissue that resides on human skin to a depth of xcx9c10-20 microns.
The present invention implements specialized microblades or microneedles to provide a conductive system for use in electrical sensing applications to replace other apparatus, such as ECG electrodes, bioelectrical patches, among others. This invention may be used in replacement of various biosensing applications needing preparation of the skin such as shaving, sanding, gelling and similar procedures to enhance physiological signal sensing.
The present invention utilizes the layer of dead skin, the stratum corneum, that is normally not more than 10-20 microns in depth and makes up the outer layer of the human skin. The invention utilizes metalized nano spikes disposed on metalized electrode(s) to penetrate through the stratum corneum into the epidermal layer and enable data transmission from the epidermal layer to electrodes configured for connection to other medical devices.
In one embodiment, the nano spikes may provide a fixed, longer-term site so that the electrode may serve as an ECG sensing electrode. The invention provides a metalized contact area equipped with metalized nano spikes to make low impedance contact, thereby allowing good electrical contact for proper ECG sensing and/or electrical drive. The metalization may be applied, after completion of standard MEMs-like knife/needle/spike construction, by vapor deposition, electrolysis, or similar metallic deposition methods. The knives/needles have a substantially thin coating of conductive metal (10-100 angstroms) and connect to a backing plate that is preferably a metalized electrode. The advantages of having these spikes (xcx9c10 microns) are that they will not contact the nerves or the capillaries that are 200 to 300 microns deep. Thus, there is little or no pain/discomfort and no bleeding. Fitting over the metalized electrode is preferably an adhesive that is commonly available through a variety of manufacturers, such as 3M. The adhesives may be useful for short term use, for example, about two days, or long term, up to a week.
In yet another embodiment, the present invention may be adapted to serve as an electroencephalogram (EEG) electrode for making contact with a patient""s head where a multiplicity of such electrodes are used. In this embodiment, a round preferably flexible substrate for each electrode is used to attach the nano spikes. These round electrodes are held in contact with the patient""s head via a xe2x80x9cnetlikexe2x80x9d structure, skull cap, helmet or similar configuration that provides pressure on the electrodes to maintain and ensure continuous contact of the electrodes with the scalp. The nano spike electrode of the present invention would advantageously replace the complex structure disclosed in the ""982 patent.
In another embodiment, the present invention is implemented as a xe2x80x9csmart patchxe2x80x9d or extended memory device to receive Body Wave and Body Bus transmissions. Specifically, the invention relates to an electrode that is compatible with extended memory devices and other peripheral devices, mounted externally to patients, to provide communication with implantable devices in the patient. As a memory patch, the device""s electrode would preferably be provided with a memory chip and a power source.
The present invention provides novel features in the implementation and use of extended memory patch as compared to disclosures in the ""265 patent, as well as body wave and body bus system disclosed in the ""636, ""897, and ""859 patents, respectively. The peripheral memory patch described in the ""265 patent enables the extension of an implantable device""s memory.
The present invention may be implemented to extend the memory capacity of implanted devices. Specifically, a memory patch may be taped either over the device (system A or B telemetry) or anywhere on the body (Body wave/bus technology in telemetry C). As the memory of the implanted device fills up, the device transmits the data to the external memory patch for storage, automatically. Such an operation allows one to perform a 24/48-hour Holter monitoring inexpensively in conjunction with or directly from implanted devices. This memory patch would only need to operate for, at most, a couple of days. These patches can be equipped with a much larger memory than what is normally found in an implantable device, thereby allowing for the storage of a greater amount of data. The procedure and process are inexpensive when particularly implemented as a tape-on, use-it-once device. Subsequently the data is downloaded and the patch thrown away. In this embodiment, the present invention uses a flexible xe2x80x9cfoilxe2x80x9d battery commonly found in credit cards. The patch can be used at home and be equipped with an LED that would light up when the memory is filled up. Subsequently, the patient would remove the patch and mail it in to the doctor or a lab for analysis.
In yet another embodiment, the present invention can be adapted to accept more than one ECG electrode to monitor cardiac events, which, in the prior art, required a minimally invasive implantable device, such as described in U.S. Pat No. 5,987,352, issued to Klein, et al. and incorporated herein by reference in its entirety. The nano spikes of the present invention are electrically connected to a metalized electrode substrate and, through, it, to the ECG electrodes. When taped on, the circuitry could be tuned to pick the best vector (largest signal). This embodiment would use electronics similar to the type described in the ""352 patent. Such electronics would be adapted to the present invention by miniaturization, and could be integrated with the metalized electrode substrate for secure placement on the patient""s body.